Study On The Control Effect Of Chlorine Dioxide On Algae And Products In Mengshan Water Plant

In recent years,the degree of eutrophication of water environment is becoming increasingly high,which has developed into one of the key environmental pollution problems worldwide resulting in the excessive breeding of algae and thenalgal blooms.Reservoir waterworks often suffer from algal bloom problems.When the concentration of algae is too high in the source water,it will affect the efficiency of coagulation and sedimentation of the filter,and lead to the blocking of the filter,the great reduction of the filtration cycles,and the increase of the proportion of algal toxins and algal disinfection by-products in the chlorinated water.The main reason why chlorine dioxide（ClO₂）can control algae is that it has a certain binding ability to the benzene ring,which can change the benzene ring without producing odor.The pyrrole ring and the benzene ring in the chlorophyll of algae cells are very similar,so C1O₂can also bind to the pyrrole ring to oxidize the chlorophyll and cause the metabolism of the algae to stop.As a strong oxidant,ClO₂has a good algae-removing effect.During the algae-removal process,it does not produce triple substances,does not increase the chromaticity of water,and reduce odor substances.This paper takes Mengshan Waterworks as a study subject which is polluted by algae;detects and analyzes its water source reservoir,Huangtushan Reservoir;and explores many factors that affect the effect of algae removal by ClO₂,the control effect of ClO₂on algae cells and extracellular organic matter,and the law of generating inorganic by-product ClO₂^-in the process of algae removal by ClO₂.Studies have shown that the Huangtushan Reservoir is already in a state of eutrophication,mainly contaminated with nutrients,algae and organic matters.The algal blooms belong to seasonal variation in Huangtushan Reservoir,mainly in summer.The algal bloom rate is the highest in July and August.The optimal species of algae in the reservoir mainly consists of oscillatoria and microcystis aeruginosa in the phylum of cyanobacteria.Studies on the effect of algae removal by ClO₂preoxidation reveal that a reasonable feeding concentration of ClO₂is about 1.0 mg/L,the contact oxidation time is about 10 minutes and the best temperature for 25°Cwhen the level of chlorophyll a is 93.95μg/L in an algal crude solution.When adding low concentration of ClO₂,algal cells have certain resistance to ClO₂,and it can only remove a small amount of algal cells.As the concentration of the added ClO₂increases gradually,the resistance of algal cells is disintegrated,and the algae removal rate increases significantly with the breakage of a large number of algal cells.When the algal stock solution is acidic,the algal removal effect by ClO₂is better than that under an alkaline condition.ClO₂control effect tests on algal cells and extracellular organics reveal that the effect of ClO₂on growth and reproduction of algae cells is excellent,and the higher the ClO₂concentration is,the better the effect of inhibiting algae activity will be.Moreover,with the increase of additional concentration of ClO₂,the content of GSM and extracellular 2-MIB increases in different ranges.The 2-MIB and GSM have increased by 6.3%and 65.1%,1.0 mg/L ClO₂oxidized chlorophyll a content of 93.95μg/L algae stock solution after 10 min.The experiments for the law in generating inorganic by-products ClO₂^-duringalgae removal by ClO₂show that the production of inorganic by-products ClO₂^-is affected by p H in raw water.The amount of ClO₂^-production goes up with the increase of p H value,and the remaining ClO₂decreases with the increase of p H value,which is rarely affected by the initial concentration of algae,the content of organic matter and the level of ammonia nitrogen.